In some fuel cell based power generators, hydrogen is extracted from a fuel in the presence of water and then is introduced into a fuel cell to produce electricity. Power generators based on hydrogen generators and proton exchange membrane (PEM) fuel cells may contain valves to control the rate at which electricity is generated. Such valves may require precision parts and be very expensive to provide adequate seals when closed. There is a need for a valve that can better control the flow of water, hydrogen and/or oxygen.